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This article examines the physical and mechanical characteristics of mixtures of two different synthetic rubbers, namely styrene-butadiene rubber (SBR) and nitril-butadiene rubber (NBR), with novolac type phenolicresin (PH). According to Taguchi experimental design method, it is shown that the addition of PH increases the crosslinking density of rubber phase probably due to its curative effects. Thermal analysis of the blends indicates that, contrary to NBR/PH blend, thermal stability of SBR/ PH blend is dependent on sulfur content due to predominant polysulfidic crosslinks formed in SBR. Slight shift in glass-transition temperature (T g ) of pure SBR and NBR vulcanizates by the addition of PH suggests that both SBR/PH and NBR/PH are incompatible blends with a partially soluble PH in the rubber phase. Two-phase morphology of the mixtures is also evidenced by scanning electron microscopy. Correlation of the rubber/PH modulus versus PH concentration by Halpin-Tsai model shows a deviation from the model. Presence of PH in the rubber phase is thought to vary the mechanical properties of the rubber phase by changing both the crosslinking density and rigidity of the molecular network of the rubber, leading to misuse of modulus of pure rubber in Halpin-Tsai equation.

Properties of melt processed polyamide 66 (PA66)/multiwalled carbon nanotube composite were first characterized experimentally. The experimental results exhibited the formation of crystalline layer around the nanotubes and a considerable enhancement in mechanical properties by incorporation of multiwalled carbon nanotube up to 1 wt%. Mechanical properties were analyzed in terms of structural parameters using micromechanical models proposed in this study. It was suggested that the mechanical properties were greatly dominated by crystalline layer and nanotube length. It was also deduced that the melt mixing process caused a significant nanotube breakage restricting further enhancement of nanocomposite properties at higher nanotube contents. Surface modification of nanotube provided better polymer-nanotube interaction; however, it increased the mechanical properties marginally.

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